Introduction

Philosophy is the study of general and fundamental problems, such as those connected with reality, existence, knowledge, values, reason, mind, and language.

Philosophy is distinguished from other ways of addressing such problems by its critical, generally systematic approach and its reliance on rational argument.

In more casual speech, by extension, "philosophy" can refer to "the most basic beliefs, concepts, and attitudes of an individual or group".

The word "philosophy" comes from the Ancient Greek φιλοσοφία (philosophia), which literally means "love of wisdom".

The introduction of the terms "philosopher" and "philosophy" has been ascribed to the Greek thinker Pythagoras.

Scuola di Atene - The School of Athens

Raffaello Sanzio da Urbino

The School of Athens, or Scuola di Atene in Italian, is one of the most famous frescoes by the Italian Renaissance artist Raphael. It was painted between 1509 and 1511 as a part of Raphael's commission to decorate with frescoes the rooms now known as the Stanze di Raffaello, in the Apostolic Palace in the Vatican. The Stanza della Segnatura was the first of the rooms to be decorated, and The School of Athens the second painting to be finished there, after La Disputa, on the opposite wall. The picture has long been seen as "Raphael's masterpiece and the perfect embodiment of the classical spirit of the High Renaissance."

Areas of inquiry

Philosophy is divided into many sub-fields.

These include epistemology, logic, metaphysics, ethics, and aesthetics.

Some of the major areas of study are considered individually below.

Epistemology

Epistemology is concerned with the nature and scope of knowledge, such as the relationships between truth, belief, and theories of justification.

Skepticism is the position which questions the possibility of completely justifying any truth.

The regress argument, a fundamental problem in epistemology, occurs when, in order to completely prove any statement P, its justification itself needs to be supported by another justification.

This chain can do three possible options, all of which are unsatisfactory according to the Münchhausen Trilemma.

One option is infinitism, where this chain of justification can go on forever. Another option is foundationalism, where the chain of justifications eventually relies on basic beliefs or axioms that are left unproven.

The last option, such as in coherentism, is making the chain circular so that a statement is included in its own chain of justification.

Rationalism is the emphasis on reasoning as a source of knowledge.

Empiricism is the emphasis on observational evidence via sensory experience over other evidence as the source of knowledge.

Rationalism claims that every possible object of knowledge can be deduced from coherent premises without observation.

Empiricism claims that at least some knowledge is only a matter of observation. For this, Empiricism often cites the concept of tabula rasa, where individuals are not born with mental content and that knowledge builds from experience or perception.

Epistemological solipsism is the idea that the existence of the world outside the mind is an unresolvable question.

Parmenides (fl. 500 BC) argued that it is impossible to doubt that thinking actually occurs. But thinking must have an object, therefore something beyond thinking really exists. Parmenides deduced that what really exists must have certain properties—for example, that it cannot come into existence or cease to exist, that it is a coherent whole, that it remains the same eternally (in fact, exists altogether outside time).

This is known as the third man argument.

Plato (427–347 BC) combined rationalism with a form of realism.

The philosopher's work is to consider being, and the essence (ousia) of things.

But the characteristic of essences is that they are universal.

The nature of a man, a triangle, a tree, applies to all men, all triangles, all trees.

Plato argued that these essences are mind-independent "forms", that humans (but particularly philosophers) can come to know by reason, and by ignoring the distractions of sense-perception.

Modern rationalism begins with Descartes.

Reflection on the nature of perceptual experience, as well as scientific discoveries in physiology and optics, led Descartes (and also Locke) to the view that we are directly aware of ideas, rather than objects.

This view gave rise to three questions:

Is an idea a true copy of the real thing that it represents ?

Sensation is not a direct interaction between bodily objects and our sense, but is a physiological process involving representation (for example, an image on the retina). Locke thought that a "secondary quality" such as a sensation of green could in no way resemble the arrangement of particles in matter that go to produce this sensation, although he thought that "primary qualities" such as shape, size, number, were really in objects.

How can physical objects such as chairs and tables, or even physiological processes in the brain, give rise to mental items such as ideas ?

This is part of what became known as the mind-body problem.

If all the contents of awareness are ideas, how can we know that anything exists apart from ideas?

Descartes tried to address the last problem by reason.

He began, echoing Parmenides, with a principle that he thought could not coherently be denied: 'I think, therefore I am' (often given in his original Latin: Cogito ergo sum).

From this principle, Descartes went on to construct a complete system of knowledge (which involves proving the existence of God, using, among other means, a version of the ontological argument).

His view that reason alone could yield substantial truths about reality strongly influenced those philosophers usually considered modern rationalists (such as Baruch Spinoza, Gottfried Leibniz, and Christian Wolff), while provoking criticism from other philosophers who have retrospectively come to be grouped together as empiricists.

Rules of inferences from premises include the most popular method, modus ponens, where given “A” and “If A then B”, then “B” must be concluded.

A common convention for a deductive argument is the syllogism.

An argument is termed valid if its conclusion does indeed follow from its premises, whether the premises are true or not, while an argument is sound if its conclusion follows from premises that are true.

Propositional logic uses premises that are propositions, which are declarations that are either true or false, while predicate logic uses more complex premises called formulae that contain variables.

These can be assigned values or can be quantified as to when they apply with the universal quantifier (always apply) or the existential quantifier (applies at least once). Inductive reasoning makes conclusions or generalizations based on probabilistic reasoning. For example, if “90% of humans are right-handed” and “Joe is human” then “Joe is probably right-handed”.

Metaphysics

Metaphysics is the study of the most general features of reality, such as existence, time, the relationship between mind and body, objects and their properties, wholes and their parts, events, processes, and causation.

Traditional branches of metaphysics include cosmology, the study of the 'world in its entirety', and ontology, the 'study of being'.

Within metaphysics itself there are a wide range of differing philosophical theories. Idealism, for example, is the belief that reality is mentally constructed or otherwise immaterial while realism holds that reality, or at least some part of it, exists independently of the mind.

Subjective idealism describes objects as no more than collections or "bundles" of sense data in the perceiver.

The 18th century philosopher George Berkeley contended that existence is fundamentally tied to perception with the phrase Esse est aut percipi aut percipere or "To be is to be perceived or to perceive".

In addition to the aforementioned views, however, there is also an ontological dichotomy within metaphysics between the concepts of particulars and universals as well.

Particulars are those objects that are said to exist in space and time, as opposed to abstract objects, such as numbers.

Universals are properties held by multiple particulars, such as redness or a gender.

The type of existence, if any, of universals and abstract objects is an issue of serious debate within metaphysical philosophy.

Realism is the philosophical position that universals do in fact exist, while nominalism is the negation, or denial of universals, abstract objects, or both.

Conceptualism holds that universals exist, but only within the mind's perception.

The question of whether or not existence is a predicate has been discussed since the Early Modern period.

Essence is the set of attributes that make an object what it fundamentally is and without which it loses its identity.

Essence is contrasted with accident: a property that the substance has contingently, without which the substance can still retain its identity.

Moral and Political Philosophy

Ethics, or "moral philosophy," is concerned primarily with the question of the best way to live, and secondarily, concerning the question of whether this question can be answered. The main branches of ethics are meta-ethics, normative ethics, and applied ethics.Meta-ethics concerns the nature of ethical thought, such as the origins of the words good and bad, and origins of other comparative words of various ethical systems, whether there are absolute ethical truths, and how such truths could be known.Normative ethics are more concerned with the questions of how one ought to act, and what the right course of action is.This is where most ethical theories are generated.Lastly, applied ethics go beyond theory and step into real world ethical practice, such as questions of whether or not abortion is correct.Ethics is also associated with the idea of morality, and the two are often interchangeable.

One debate that has commanded the attention of ethicists in the modern era has been between consequentialism (actions are to be morally evaluated solely by their consequences) and deontology (actions are to be morally evaluated solely by consideration of agents' duties, the rights of those whom the action concerns, or both). Jeremy Bentham and John Stuart Mill are famous for propagating utilitarianism, which is the idea that the fundamental moral rule is to strive toward the "greatest happiness for the greatest number", however, in promoting this idea they also necessarily promoted the broader doctrine of consequentialism.Adopting a position opposed to consequentialism, Immanuel Kant argued that moral principles were simply products of reason.Kant believed that the incorporation of consequences into moral deliberation was a deep mistake, since it denies the necessity of practical maxims in governing the working of the will.According to Kant, reason requires that we conform our actions to the categorical imperative, which is an absolute duty.

Political philosophy is the study of government and the relationship of individuals (or families and clans) to communities including the state.It includes questions about justice, law, property, and the rights and obligations of the citizen.Politics and ethics are traditionally inter-linked subjects, as both discuss the question of what is good and how people should live.From ancient times, and well beyond them, the roots of justification for political authority were inescapably tied to outlooks on human nature.In 'The Republic', Plato presented the argument that the ideal society would be run by a council of philosopher-kings, since those best at philosophy are best able to realize the good.Even Plato, however, required philosophers to make their way in the world for many years before beginning their rule at the age of fifty.For Aristotle, humans are political animals (i.e. social animals), and governments are set up to pursue good for the community.Aristotle reasoned that, since the state (polis) was the highest form of community, it has the purpose of pursuing the highest good.Aristotle viewed political power as the result of natural inequalities in skill and virtue. Because of these differences, he favored an aristocracy of the able and virtuous.For Aristotle, the person cannot be complete unless he or she lives in a community.His 'Nicomachean Ethics' and 'Politics' are meant to be read in that order.The first book addresses virtues (or "excellences") in the person as a citizen; the second addresses the proper form of government to ensure that citizens will be virtuous, and therefore complete.Both books deal with the essential role of justice in civic life.Thomas Hobbes also contested many elements of Aristotle's views.For Hobbes, human nature is essentially anti-social: people are essentially egoistic, and this egoism makes life difficult in the natural state of things.Moreover, Hobbes argued, though people may have natural inequalities, these are trivial, since no particular talents or virtues that people may have will make them safe from harm inflicted by others.For these reasons, Hobbes concluded that the state arises from a common agreement to raise the community out of the state of nature.This can only be done by the establishment of a sovereign, in which (or whom) is vested complete control over the community, and is able to inspire awe and terror in its subjects.Many in the Enlightenment were unsatisfied with existing doctrines in political philosophy, which seemed to marginalize or neglect the possibility of a democratic state.Jean-Jacques Rousseau was among those who attempted to overturn these doctrines: he responded to Hobbes by claiming that a human is by nature a kind of "noble savage", and that society and social contracts corrupt this nature.Another critic was John Locke.In 'Second Treatise on Government' he agreed with Hobbes that the nation-state was an efficient tool for raising humanity out of a deplorable state, but he argued that the sovereign might become an abominable institution compared to the relatively benign unmodulated state of nature.Following the doctrine of the fact-value distinction, due in part to the influence of David Hume and his student Adam Smith, appeals to human nature for political justification were weakened.Nevertheless, many political philosophers, especially moral realists, still make use of some essential human nature as a basis for their arguments.Marxism is derived from the work of Karl Marx and Friedrich Engels.Their idea that capitalism is based on exploitation of workers and causes alienation of people from their human nature, the historical materialism, their view of social classes, etc., have influenced many fields of study, such as sociology, economics, and politics.ÆstheticsAesthetics (also spelled æsthetics) is a branch of philosophy dealing with the nature of art, beauty, and taste, with the creation and appreciation of beauty.It is more scientifically defined as the study of sensory or sensori-emotional values, sometimes called judgments of sentiment and taste.More broadly, scholars in the field define aesthetics as "critical reflection on art, culture and nature."More specific aesthetic theory, often with practical implications, relating to a particular branch of the arts is divided into areas of aesthetics such as art theory, literary theory, film theory and music theory.Philosophy of MindPhilosophy of mind is a branch of philosophy that studies the nature of the mind, mental events, mental functions, mental properties, consciousness, and their relationship to the physical body, particularly the brain.The mind-body problem, i.e. the relationship of the mind to the body, is commonly seen as one key issue in philosophy, although there are other issues concerning the nature of the mind that do not involve its relation to the physical body, such as how consciousness is possible and the nature of particular mental states.Dualism and monism are the two major schools of thought that attempt to resolve the mind-body problem.Dualism can be traced back to Plato, but it was most precisely formulated by René Descartes in the 17th century.Substance Dualists argue that the mind is an independently existing substance, whereas Property Dualists maintain that the mind is a group of independent properties that emerge from and cannot be reduced to the brain, but that it is not a distinct substance.Monism is the position that mind and body are not ontologically distinct kinds of entities. This view was first advocated in Western philosophy by Parmenides in the 5th century BC Physicalists argue that only the entities postulated by physical theory exist, and that the mind will eventually be explained in terms of these entities as physical theory continues to evolve.Idealists maintain that the mind is all that exists, and that the external world is either mental itself, or an illusion created by the mind.Neutral monists such as Ernst Mach and William James argue that events in the world can be thought of as either mental (psychological) or physical depending on the network of relationships into which they enter.